1. Field of the Invention
The present invention relates to an image forming apparatus using an electrophotographic photoconductor and an image forming method using such an image forming apparatus, and more particularly to an image forming apparatus which can maintain the excellent image characteristics by leveling particles using a predetermined leveling means when the particles remain on a surface of the electrophotographic photoconductor, and an image forming method which uses the image forming apparatus.
2. Related Art
Conventionally, an image forming apparatus which is used in a printer, a copying machine or the like adopts an image forming process which is configured by sequentially arranging, around an electrophotographic photoconductor, a charging means which charges the electrophotographic photoconductor, an exposing means which form a latent image by exposing a surface of the charged photoconductor, a developing means which develops the latent image by transferring a toner to the latent image, a transferring means which transfers the toner to a recording paper thus visualizing an image, and a charge eliminating means which erases a residual potential which remains on the surface of the photoconductor after transferring the toner.
Here, as the charging means, there have been known a contact charging method which brings a charging member such as a charging roller or the like into direct contact with the surface of the electrophotographic photoconductor, and a non-contact charging method which corona-charges the surface of the photoconductor using a corona charger. Due to the simple overall constitution and no generation of harmful substances such as ozone, the non-contact charging method has been put into practice more frequently.
However, in this contact charging method, the surface of the electrophotographic photoconductor and the charging member are directly brought into contact with each other and hence, there has been observed a phenomenon that particles which constitute developer components remaining on the surface of the photoconductor after printing are adhered to the surface of the charging member thus generating charging irregularities. Such charging irregularities lower a charging potential of the surface of the electrophotographic photoconductor after passing the charging means thus becoming one of causes of the so-called transfer memory in which a potential having polarity opposite to the charged polarity remains on the surface of the photoconductor after the transferring of the toner.
Accordingly, to overcome such a drawback, as shown in FIG. 8, there has been proposed an image forming apparatus 100 which uses a contact-type charging means 102 as a charging means and also includes a cleaning means 111 for cleaning a charged surface of the charging means 102 so as to remove foreign substances which are adhered to the charged surface (see patent document 1, for example).
Further, as shown in FIG. 9, there has been also proposed an image forming apparatus 200 which adopts an inversion developing method in which the image forming apparatus 200 includes a contact-type primary charging roller 202, a developing means 204, a transferring means 206 and a front exposure lamp 209, wherein the image forming apparatus 200 further includes a contact-type pre-charging roller 208 which is charged to the same polarity as the charging roller 202 upstream of the charging roller 202 (see patent document 2, for example). Due to such a constitution, a surface of a photoconductor which is charged with the polarity opposite to the polarity of the contact-type primary charging roller 202 is pulled up to the same polarity by the pre-charging roller 208 thus erasing the transfer memory.    [patent document 1] JP-4-60660 (claims, FIG. 1)    [patent document 2] JP-6-83249 (claims, FIG. 1)